The present invention relates to a liquid container of an air open type which is suitable as an ink cartridge to be attached to an ink jet printer, for example, and a liquid filling method of filling the liquid container with a liquid.
Examples of a liquid container include an ink cartridge to be used in a printer of an ink jet type. The ink cartridge for the printer of the ink jet type has an ink chamber, provided in a container body, for accommodating an ink to be supplied to a print head. The ink cartridge can be removably fitted and attached into a cartridge attachment portion at a predetermined position in use. The ink accommodated in the ink chamber is supplied to the print head to be driven in accordance with print data transferred from a host computer and is ejected onto a target position of a print medium, such as a paper, by means of a nozzle provided on the print head.
As an ink cartridge of an air open type to be attached to the printer of the ink jet type, there has variously been proposed a structure comprising: a container body attachable to an ink receiving portion of a printer side; an ink chamber for accommodating an ink; an ink supply hole provided to communicate with the ink chamber and connectable to the ink receiving portion of a cartridge attachment portion of the printer side; an ink leading path for leading the ink stored in the ink chamber to the ink supply hole; pressure regulating means provided in a portion of the ink leading path and serving to regulate a pressure of the ink to be supplied to the ink receiving portion through the ink supply hole; and an air open passage for causing the ink chamber to communicate with an outside, thereby introducing outside air into the ink chamber as the ink in the ink chamber is consumed.
For such an ink cartridge, there has been proposed a liquid filling method of previously forming, in a container body, a special ink injecting hole communicating with an ink chamber and filling the ink chamber with an ink by using the ink injecting hole (see Patent Document 1, for example).
Patent Document 1: JP-A-2004-216866
Patent Document 2: JP-A-2005-22257
The special ink injecting hole for filling the ink is provided for the following reasons.
In case of the ink cartridge as discussed above, two holes, i.e. an air open hole and an ink supply hole, are provided for causing the ink chamber to communicate with an outside. However, neither of these two holes is suitable for injecting the ink. In other words, the air open hole usually has a very small passage diameter or cross-sectional area, and furthermore, has such a complicated structure that bending is repeated many times in order to prevent the ink from easily leaking out even if the cartridge is vibrated or the like in use. For this reason, the ink cannot be caused to flow quickly through the air open hole. When the stuck ink is dried later, moreover, there is also a possibility that an original function of the air open hole might be deteriorated due to clogging. On the other hand, a passage diameter or cross-sectional area of the ink supply hole can be set to be larger than that of the air open hole, but pressure regulating means is provided in an ink leading path causing the ink supply hole to communicate with the ink chamber. Since the pressure regulating means has a function as a nonreturn valve for hindering a reverse flow from the ink supply hole side to the ink chamber, it is difficult to use the ink supply hole to fill the ink into the ink chamber.
In the structure in which the special ink injecting hole is provided as described above, however, it is necessary to comprise a step of sealing the opened ink injecting hole by sticking a seal film after completing the ink filling step. The step of sealing the ink injecting hole causes an increase in the steps of manufacturing the ink cartridge. Consequently, a cost is increased or a productivity is deteriorated.
When the ink injecting hole is provided, moreover, there is a possibility that a user might peel the seal film sealing the ink injecting hole by mistake, thereby causing a disadvantage such as a leakage of the ink.
Furthermore, the ink cartridge may be provided with ink detecting means in a portion of the ink leading path and upstream of the pressure regulating means. In this case, the ink detecting means may be configured to oscillate a piezoelectric oscillator and to detect a state in which the ink in the ink leading path is replaced with air by a change in an oscillating characteristic, for example. With this type of the ink detecting means, the entry of the air into the ink leading path is regarded as an ink end or ink near end occurring when the ink in the ink chamber of the ink cartridge is fully consumed and the air introduced from the air open hole into the ink chamber thus enters the ink leading path. A detection signal sent from the ink detecting means can be utilized for displaying a residual amount of the ink and giving a notice of a time for an exchange of the cartridge.
In the case in which the ink detecting means is provided, however, there is a possibility that the ink detecting means might carry out an erroneous detection due to the air remaining in the ink leading path from the ink chamber to the ink detecting means when use is started if the ink filled in the ink chamber through the special ink injecting hole does not reach the ink detecting means provided in the portion of the ink leading path.